Minimally-invasive intracardiac ablation is the treatment of choice for various types of arrhythmias. To perform such treatment, the physician typically inserts a catheter through the vascular system into the heart, brings the distal end of the catheter into contact with myocardial tissue in areas of abnormal electrical activity, and then energizes one or more electrodes at or near the distal end in order to create tissue necrosis.
A number of systems for probe-based medical procedures, such as, for example, intracardiac ablation therapy, are commercially available, such as the CARTO™ system offered by Biosense Webster Inc. (Diamond Bar, Calif.). CARTO tracks the position and operating parameters of the distal end of the catheter and displays this information electronically on a three-dimensional (3D) anatomical map of the heart. CARTO enables the system operator to electronically tag locations that have been ablated on the map and thus to keep track of the progress of the procedure.
To apply a catheter-based procedure, the physician typically forces the catheter towards the heart inner surface tissue (myocardium). If during the medical procedure (e.g., ablation) the catheter exerts a force upon the tissue that is higher than the force the tissue can tolerate, the catheter may eventually perforate the tissue. As a result, blood or other fluids filling the heart chamber may flow through the perforated tissue to fill up the space between the heart and the pericardium (i.e., the pericardial cavity), a situation referred to as cardiac tamponade.
U.S. Pat. No. 6,351,667, whose disclosure is incorporated herein by reference, describes an apparatus for detecting pericardial effusion that includes a measurement apparatus connected to a wire probe to be anchored on the right heart ventricle and to two other wire probes to be anchored in different regions of the pericardial sac. The measurement apparatus measures and displays the change in impedance between the individual wire probes.
European Patent Application Publication EP 2248480, whose disclosure is incorporated herein by reference, describes various embodiments that predict the volume, area and/or depth of lesions created through the use of a force-time integration technique. Other embodiments control the energy delivered to the ablation probe based on the contact force between the ablation probe and the target tissue to prevent steam popping. In another aspect, various embodiments of the invention reliably visualize the predicted volume, area and/or depth of lesions created during ablation procedures. One embodiment visualizes the predicted lesions created utilizing a force contact density mapping procedure. Another embodiment visualizes the predicted lesions through the use of a force-time integration technique. Yet another embodiment visualizes the predicted lesions through the use of a force time and power (and/or current) integration technique. Other embodiments predict the occurrence and locations tissue damage such as perforation that occurred during the ablation process. Still other embodiments predict the occurrence and location of isolation gaps that may occur during or after the procedure.
European Patent EP 1229829, whose disclosure is incorporated herein by reference, describes a system for detecting the presence of a perforation in a body cavity. The system includes a fluid pressure source; a medical device insertable into a body cavity, the medical device fluidly coupled to the fluid pressure source for delivery of fluid to the body cavity; and a pressure sensor positioned to detect a pressure of the fluid delivered to the body cavity.